Most repeating firearms generally utilize a “rotary lock-up” bolt locking system in which a locking member rotates about a centerline of the barrel assembly, engaging and disengaging tabs or lugs with mating surfaces in the barrel assembly. The tabs, or lugs, traditionally have been integral components of the bolt head and are required to support the rearward axial load produced by the shell or cartridge when fired. As a result of this integral design, the entire bolt head assembly is required to rotate to engage and disengage the lugs. Firearms further must incorporate an extractor to pull the shell or cartridge out of the chamber when the bolt is opened, which extractor typically is mechanically attached the bolt head so as to rotate as an integral component of the bolt head assembly.
In the case of shotguns, the extractor is an appendage that extends beyond the face of the bolt head and as a result requires axial and radial clearances be formed in the barrel to accommodate such movement. Machining such radial clearances in the barrel has been and continues to be a difficult operation in the manufacture of rotary lockup barrel assemblies. Typical centerfire rotary lock up bolt assemblies therefore have recessed the extractor within the bounds of the bolt head to eliminate the requirement for axial or radial clearances in the barrel. In either case, the extractor engages the rim of the shell when the firearm is locked up and upon rotation of the bolt head from unlocked to locked or from locked to unlocked, the extractor must slide along the outside diameter surface of the shell or cartridge. Depending on the mechanical interface of the extractor and rim of the shell or barrel, significant malfunctions accordingly can occur. Ideally, the extractor engages the rim of the shell upon close up of the firearm and should remain stationary relative to the cartridge through the entire extraction process, thus reducing the potential for extraction malfunctions and as well as significantly reducing the difficulties in the manufacture of barrels with such axial and/or radial clearance for extractors.
Accordingly, it can be seen that a need exists for a bolt assembly and locking system for firearms that addresses the foregoing and other related and unrelated problems in the art.